The Convergence of the Tritanopic Confusion Loci and the Derivation of the Fundamental Response Functions

SUMMARY1. Eight deuteranopes matched a mixture of a monochromatic light on the long wave side of the neutral point and a violet (450 nm) primary to a fixed white as well as a monochromatic light on the short wave side of the neutral point mixed with a red (650 nm) primary, to the same white. For A > 530 nm, the former set of matches defined the action spectrum of the long wave sensitive foveal cones, and for A < 480 nm, the latter that of the short wave sensitive cones.2. Individual differences in the former matches were approximately correlated with the respective ratio of the sensitivities of the wave-length of the anomaloscope primaries, in a way that individual differences of the latter were not.3. Assuming that eye media differences alone account for the differences in long wave sensitive foveal action spectra, the spectral reflectivity of the foveal fundus was predicted for these deuteranopes. The prediction is inconsistent with measurement.4. Thirteen deuteranopes matched monochromatic spectral lights with a green (535 nm) and a blue (460 nm) primary. The results were analysed by von Kries' method in which differences in matching due to differences in eye media absorption are obviated. The matches of five differed significantly from one another when so analysed. It was concluded that at least one of the two action spectra of the foveal cones of every one of these five differed from that of all of the others.5. The canon that deuteranopes accept normal colour matches was evaluated by confronting a single normal with five deuteranopes in the analytical anomaloscope of Baker & Rushton, set in the mode of each of the five in turn. Obvious differences existed between this normal's matches and those of four of five deuteranopes.

Section: Discussionmentioning

confidence: 99%

Variation in the action spectrum of erythrolabe among deuteranopes.

Alpern¹,

Pugh²

1977

“…The hypothesis of reduction dichromacy means that such lines should be concurrent in a point, the 'tritanopic confusion locus'. The usual procedure (Thomson & Wright, 1953;Sperling, 1960;Alpern, 1976) is to identify from the plots of chromaticity co-ordinates (Fig. 3) pairs of wave-lengths -one on the long-wave, the other on the short-wave side of 450 nm -which have identical tritanopic chromaticities.…”

Section: Nagel Anomaloscopementioning

confidence: 99%

Classical tritanopia

Alpern

Kono

Krantz

1983

6. Colour matches made by the trichromatic eye do not match when viewed by the tritanopic eye, almost certainly because the ocular media of the two eyes have wave-length-dependent differences in absorption. For the largest difference (430 nm) the trichromatic eye transmits about 2-2 times more light than its fellow. When allowance is made for these differences, the field sensitivities of n4 and H5 of the two eyes do not differ. The field sensitivities of n4 and H5 of the normal eye, on the other hand, differ significantly from those of the average spectra obtained on four normal trichromats by Stiles, in a way that cannot be attributed to differences in transmittance of ocular media.7. It is concluded that classical (or acquired) tritanopia is not distinguishable in its

“…Baylor & Hodgkin, 1974;Norman & Werblin, 1974;Hood & Hock, 1975), and some psychophysically observed adaptation is thus very likely to occur in the photoreceptors. Secondly, the HI-mechanisms are readily grouped into three classes, (H1, H2, H3}', H4, H141} {H5, H51} according to spectral region of maximal sensitivity: the three maxima correspond well with those deduced for the trichromatic fundamentals on the basis of Koenig's loss theory of dichromacy (Pitt, 1944;Thomson & Wright, 1953) and well with the limited microspectrophotometric evidence on the absorption spectra of individual human and primate photoreceptors. Thus, each of the three classes of I-mechanisms would appear to be closely linked with one fundamental.…”

Section: Introductionmentioning

confidence: 67%

“…0, = K2fl, + K3yc.. The assumed a spectrum is considerably narrower and steeper in the long wave-lengths than the 'blue-fundamental' of Thomson & Wright (1953) or the virtually identical short-wave-length 'receptor primary' of Vos & Walraven (1951). The 0E spectrum is approximately that 743 of the spectral luminosity curve, with ,8,y7,, the receptor primaries and K2 = 0O591, K3 = 0-635, the weighting coefficients of Vos & Walraven (1971):No special significance need be attributed to this assumption about ;,: the essential aspects of the assumption are that the peak of the @,c spectrum is equal to that of the secondary mode of H1, and that below 550 nm of the Ai spectrum declines monotonely.…”

Section: Resultsmentioning

confidence: 98%

The nature of the pi1 colour mechanism of W.S. Stiles.

Pugh¹

1976

SUMMARY1. The Ill colour mechanism was isolated by means of Stiles's auxiliary field technique: that it is H1l which is isolated is proven by both test and field action spectra.2. The fundamental mechanisms of human trichromatic colour vision must satisfy Grassmann's law of additivity. The hypothesis that H., is one of the three fundamentals is tested by experiments in which pairs (Al, /s2) of monochromatic adapting fields are mixed.3. When two fields with wave-lengths in the neighbourhood of its primary mode (JU., #t2 < 500 nm) are combined, HIl is field-additive, consistent with the hypothesis that this portion of the H1 action spectrum is that of the short-wave-length-sensitive photoreceptors.4. When a short-wave-length adaptation field (tl . 500 nm) is mixed with a longer wave-length field (qu2 > 550 nm) H1 is strongly non-additive. This result proves that the long-wave-length portion of the Hl field spectrum is generated at least in part by a signal originating in the long-or middle-wave-length sensitive cones.5. Analysis of the additivity failures supports a model of H, in which the signal to be detected is generated in the short-wave-length cones, and must pass serially through two gain stages: the gain in the first stage is controlled by the short-wave-length cones alone; the gain in the second stage is controlled by a signal originating in the middle, or long-wavelength cones, or both.